Sulfonation of fatty acids and their esters



June 14, 1966 w. STEIN ETAL 3,256,303

BYEULM DLL-Kufe 5 AOR YS United States Patent 3,256,303 SULFNATEON 0FFATTY ACIDS AND THEIR ESTERS Werner Stein, Dusseldorf-Holthausen,Herbert Weiss, Cologne-Deutz, and Otto Koch, Hilden, Rhineland, Germany,assignors to Henkel & Cie. G.m.b.H., Dusseldorf-Holthausen, GermanyFiled May 15, 1962, Ser. No. 194,840 Claims priority, applicationGermany, Aug. 8, 1961,

H 4 58 Claims. (Cl. 2450-400) This invention relates to new and usefulimprovements in the sulfonation of fatty acids and their derivatives.The invention more particularly relates to an improved process forsulfonating fatty acids or ltheir derivatives, such as their esters ornitriles, using an excess of sulfur trioxides gas as the sulfonationagent.

sulfonates of fatty acids and of fatty -acid derivatives, su-ch asesters or nitriles, constitute commercially valuable materials due toVtheir surface-active characteristics and resistance to hard water whichrender the same suitable as detergents and wetting agents. Thesesulfonates are conventionally produced by the sulfonation of thecorresponding fatty acids or fatty acid derivatives. When sulfonatingthese materials using an excess of gaseous sulfur trioxide, the reactionproducts produced were dark colored, brown-black products which, due tothis discoloration, were unsuitable for commercial use. While it waspossible to obtain somewhat lighter colored products by operating undermilder conditions of temperature, as for example 60-65 C., the use ofthese temperatures could not produce the satisfactory degree ofsulfon-ation, and when the temperature was increased, in order to obtainmore completely sulfonated products, then the darker colored reactionpro-ducts were produced. While it was possible to recover utilizablesulfonates from these dark colored reaction products byrecrystallization thereof in the form of their alkali metal salts, thisincreased the pro- 'duction costs and presented technical diiculties.

One object of this invention is the obtaining of lighten coloredreaction products, after the extensive sulfona-tion of fatty acids ortheir derivatives, using gaseous sulfur trioxide, as the sulfonationagent.

rl`hese and still further objects will become apparent from thefollowing description read in conjunction with the drawings in which:l

FIG. 1 diagrammatically shows an embodiment of an apparatus foreffecting the sulfonation in accordance with sulfonated to lightercolored reaction products using -anv excess of gaesous S03 as thesulfonation agent if the sulfonation is initially effected at atemperature not exceeding 70 C. and using not more than about 65-90% ofthe total S03 quantity and, if, thereafter the sulfonation is continuedpreferably in a further sulfonation step or steps at a temperature above70 C. using the remainder of the sulfur trioxide. Preferably thesulfonation is initially effected in a first sulfonation step at atemperature between 30 and 70 and preferably 40-65 C., using not morethan 65*90% of a l.l to 1.8 and preferably 1.2 to 1,6 molar quantity ofS03 based on the fatty acid radicals to be sulfonated .and thereafterthe sulfonation is concluded in one or more additional separatesulfonation steps at a ICC temperature between about and 95 C. andpreferably -90" C., using the balance of said molar quantity. If morethan two sulfonation steps are used, the temperature is preferablyprogressively increased within the range indicated from step to step.

The starting materials processed, in accordance with the invention, arefatty acids or their derivatives, such as esters or nitriles which maybe of any origin `and contain fatty acid radicals with y6-28, andpreferably 8-18 carbon atoms. These fatty acid radicals may come fromthe natural fats of plants, landor water-animals. Through selection ofthe starting fats it is possible to extensively influence the propertiesof lthe sulfonates to be produced. Thus, from the fats whichpredominantly contain fatty acids with l014 carbon atoms per fatty acidradical, such as from the fats of the lauric acid group which areparticularly rich in fatty acids with l2 carbon atoms, products whichare soluble at lower temperatures of, for example, 20-45 C., areobtained, while from other fats which predominantly contain fatty acidswith l6-18 and more carbon atoms per fatty acidradical, for example fromother plant fats than the above named, or from tallow or from whale andfish oils, products are obtained which are particularly well suited foruse at temperatures within the range of 50100 C.

The starting materials, .e. the fatty acids and their derivatives, suchas their esters or nitriles, should not contain apart from thealpha-position hydrogen atom, other sulfatizable or sulfonatable groups,such as forexample double-bonds or alcoholic hydroxyl-groups. The fattyacid esters to be processed in accordance with the invention may bederived from monoor polyvalent alcohols, particularly from monototrivalent-alcohols, and, as mentioned above, must not contain lanyalcoholic hydroxyl groups or other sulfatizable or sulfonatable groups.As far as the fatty acid esters of monovalent primary aliphatic alcoholsare concerned, the radical may con-tain- 1-20 carbon atoms in themolecule. Thus, for example, the esters of fatty acids with methyl tononyl-alcohols may be used. It is also possible to use fatty acid esterswhich contain radicals of such still higher alcohols'in the molecule asfor example are produced by reduction of the initially mentioned fattyacids or fatty acid mixtures, or synthetically in some other manner.Examples of readily available esters of fatty acids with higher fatalcohols include the hydrogenation products of the oleyloleate occurringin the sperm oil or the naturally occurring or synthetically producedwax esters.

Many fats, particularly those of natural origin, and the fatty acids andtheir derivatives produced therefrom often contain accompanyingsubstances, which, upon sulfonation produce strongly coloreddecomposition products. Although it is also possible to bleach thesedecomposition products according to a process mentioned hereinafter, itis advisable not to burden the sulfonation and the bleaching processthrough the decomposition products of such accompanying substances,which may be forthwith removed from .the fats and/ or the therefromproduced fatty `acids or their derivatives before the sulfonation.Examples ofV products which give with the sulfonation agent stronglycolored impurities include unsaturated fatty acids or fatty acidderivatives. Therefore, the fats to be processed are to be, as far aspossible, extensively saturated, i.e., they are to have iodine numbersbelow 5, preferably below 2.

The starting fatty acids to be sulfonated are preferably in the form ofdistillates as are the fatty acid derivatives, insofar as these aredistillable under the technical prerequisites in each case. Ifdistillation is not practical on account of a high boiling point or forother reasons, such as for example in the case of triglycerides, then itis advisable to initially remove the impurities present in the startingmaterial to be sulfonated in another manner. Thus, for example, in thecase of the natural fats, and particularly the natural triglycerides,albuminous substances and slimy substances (mucins) should be separatedin the deacidification and refining of the oils in a manner known perse.

These starting materials are preferably pr-ocessed in the absence ofinert solvents.

The total quantity of sulfur-trioxide to be used, is inter alia,dependent on the starting material to be sulfonated, and in generalranges from 1.1-1.8, preferably 1.2-1.6 m-ol sulfur-trioxide per molfatty acid radical. The quantity of the sulfur-trioxide applicable foras extensive as possible a sulfonation increases somewhat with the sizeof the fatty acid radical and in connection with monovalent alcoholesters, greatly increases with the size of the alcohol radical.

The sulfonation in accordance with the invention is effected in at leasttwo reaction steps with the first reaction step conducted attemperatures between 30 and 70 and preferably between 40 and 65 C. andthe second reaction 4step conducted at temperatures within the range of75-95 and preferably 80-90 C. It is advisable to let the temperaturesrise gradually so that the sulfur trioxide is constantly consumed andthe temperature-limit of 70 C. is only exceeded after at least 50%preferably at least 65% of the total sulfur trioxide quantities havebeen used. In the sulfonation of Cm-Cls-fatty acids, their triglyceridesand esters with monovalent C1-C5 alcohols, 1.2-1.6 mol sulfur-trioxideper mol fatty acidl radical are required for an extensive sulfonationand preferably 70- 85% -of this total are added before the 70 C.temperature is exceeded.

The sulfur trioxide is used in mixture with inert gases, such as forexample air, nitrogen, carbonio acid, etc. and these mixtures maycontain 2-40 volume percent, preferably 3-20 volume percent, sulfurtrioxide.

. The sulfur-trioxide addition and the course of the temperature areadjusted in dependence on one another and the time so that the sulfurtrioxide added reacts as extensively as possible. The rst reaction stepis to be conducted over a longer reaction period than the second stepwith the latter requiring not more than l/s-t of the total reaction timebut not less than about 5 and preferably not less thanA-15 minutes. Ifduring the entire reaction time, the velocity of the sulfur trioxideaddition is kept constant, then the second reaction step needs at most1/3 of the entire reaction time. However, it is possible to stillfurther shorten the reaction time in the second step through increasedvelocityof the sulfur trioxide addition. The first step may also beeffected with a non-uniform addition of the sulfur trioxide. Thus, forexample, it is possible to charge approximately 30-60% of thetheoretically necessary sulfur trioxide quantity within a short time atthe start of the reaction. This addition may if desired, take place atbelow the reaction temperature in the cooled starting material and thenafter the start of lthe reaction and its becoming faster with thetemperature rise an amount of sulfur trioxide is added which willreplace the amount being consumed in the reaction.

The velocity of the sulfur trioxide may be varied through the owvelocity of the sulfur trioxide and/ or in the case of sulfur trioxideinert gas mixtures through their concentration.

The reaction time depends on the starting material, on the sulfurtrioxide quantity used, and on the temperature of the reaction. Ingeneral, times between and 150 minutes, preferably between 40 and 120minutes, are to be used.

The products obtained in accordance with the invention' are sometimesstill colored brown. However, they contain, assuming comparableconditions, such as for example equal degrees of sulfonation and equalsulfonation agent excesses, much less colored impurities than theproducts produced according to known processes. Theyl may thus beconverted with much smaller bleaching agent quantities intolight-colored unobjectionable products.

The bleaching of the acid sulfonation products may be carried outaccording to copending application Serial No. 194,998 tiled the same dayherewith by treatment with hydrogen peroxide in amounts of 0.2-6 weightpercent and preferably 1-4 weight percent hydrogen petroxide, calculatedas 100% product. With the sulfonation products in accordance with theinvention, it is possibleto manage in general with less than 4% andfrequently less than 3% so far as the processed starting materials Vdidnot contain any impurities of accompanying substance, forming in thesulfonation colored decomposition products. The hydrogen peroxide ispreferably charged as 20-75 weight percent product and particularly as30-50 weight percent product. Furthermore, it is advisable to so choosethe concentration of the hydrogen peroxide to be used in dependence onits quantity that the sulfuric acid, formed at the start of thebleaching process from free sulfur trioxide and the Water quantityintroduced with the hydrogen peroxide, is n-ot more diluted than a 20%su-lfuric acid. Preferably this sulfuric acid, mathematicallyconsidered, should represent a mixture of sulfur trioxide and water witha sulfur trioxide content up to 95 weight percent and preferably up to-50 weight percent. The bleaching is effected at temperatures within therange of 20-100 and preferably of 40-80 C. i

insofar as fatty acids are sulfonated in accordance with the invention,the products produced may be converted into esters in a manner known perse. As esterication components the monoor polyvalent alcohols present asalcohol components in the initially mentioned fatty acid esters may beused. This esteriiication is desirable above all for the production ofthe esters from sulfo-carboxylic acids and monovalent alcoholscontaining at least 6 carbon atoms because the esters per se when usedas startin-g materials fo-r the sulfonation react slower withinincreasing magnitude of the alcohol radical and good degrees ofsulfonation are obtainable only with greater quantities of sulfurtrioxide.

The esteriiication of the acid sulfonation products may take placebefore or after the bleaching. If the bleached su-lfo-fatty acids areused, then the mono-salts neutralized at the sulfo-'acid group may alsobe processed.

The sulfonation is preferably carried out continuously i in such amanner that the starting material is passed through reaction zones, inwhich the temperature is raised from zone to zone, and in which,according to the proportion of the consumption, sulfur trioxide isdissolved in the starting material.

The apparatus according to FIG. 1 may, for example, be used for thecarrying out of the process. The reaction vessel consists of the pipe 1,which is divided through partitions 2 into reaction zones. Thesepartitions are here shown as sieve bottoms but, of course, in theirplace other separations which permit a owing through of the material tobe sulfonated from above downwardly and of the sulfur trioxide inert gasmixture from below upwardly may be used. The reaction zones may also beprovided with contact improving installations, such as for example,filling bodies, bellor sieve-bottoms or other known installations, whichimprove the contact between gas and liquid wherein the liquid to besulfonated lls the Zones more or less completely, or, for example, intrickling through vessels with bottom type installations only occupies asmall part of the vessel space. Each reaction zone is surrounded by atemperature jacket 6 which hasl an inlet and an outlet 7 and 8 for theheat exchange agent. At the lower end of each reaction zone a line 9leads into the reaction chamber, through which the sulfur trioxide inertgas mixture is introduced. The starting material to be processed ispassed through the line 4 into the head of the reaction vessel by meansof the distributor 5 in the form of a sprinkler, a sprayer nozzle or thelike. The material then ilowsthrough the individual reaction zones,

in which it is brought in contact with the freshly introduced sulfurtrioxide, passed through the lines 9, in proportion with the progressingsulfonation. The sulfonated material runs off through the line 11 andthe valve 12.

FIG. 2 shows a variant of the reaction zones according to FIG. 1. Hereeach reaction zone is defined by an independent vessel connected 'behindthe other in series. The advantage of the working with the devicesaccording to FIG.- 2 consists therein that in each reaction zone theinert gas free fram the sulfur trioxide is drawn off through the line10. In FIG. 2 substantially the same reference numbers are used as inFIG. 1.

FIG. 3 shows a device, as it has proved suitable for both production andlaboratory scale carr/ing-out of the process. The reaction vessel 13 issurrounded by a temperature jacket 6 with the inlet and outlet 7 and 8.Into the reac-tion vessel lead the lines 14 and 15 with the valves 16and 17, through which the material to be sulfonated and the sulfurtrioxide inert gas mixture are introduced. The inert gas, free fromsulfur trioxide, leaves the reaction vessel through the line 19, and theprocessed material passes out, through the overflow 1.8 at a ratecorresponding to the rate of introduction of new material into thereaction vessel. The overliow 18 is connected to the inlet 4 of afurther series connected reaction vessel of identical construction andseveral such vessels may be series connected.

The following examples are given by way of illustration and notlimitation:

Example 1 For the carrying out of the process described here, 5 vesselsaccording to FiG. 3 are connected one after another in series. Thecontent of each vessel up to the over-iiow amounts to 40 ccm. Asstarting material, there is used a lauric acid methyl ester, which hadbeen obtained from a coconut-oil hardened to an iodine number of 0.2 andesteried with methyl alcohol followed by fractionating'out of the lauricacid methyl ester.

The first four reaction vessels were filled with this ester and theheating adjusted so that the reaction mixture present in the vessels hadduring the entire test the following temperatures, increasing fromvessel to vessel: 1st vessel: second vessel: 60, third vessel: 70;vfourth vessel 80, fifth vessel: 80 C. Sulfur trioxide, diluted with a20-fold quantity of air was blown in the first four vessels in suchquantities that in the individual Vessels the following sulfur trioxidequantities were taken up, in percent of the stoichiometrically necessaryquantity for a quantitative sulfonation: 1st: 52, 2nd: 78, 3rd: 104, and4th: 130%. No sulfur trioxide air mixture was blown 'into the 5thvessel. After these quantities had been taken up, 107 g. ester per hourwas continuously introduced drop by drop into the first vessel and somuch of the above-mentioned sulfurtrioxide air mixture was introducedinto the first four vessels that the total quantity of the sulfurtrioxide introduced amounted to 1.3 mol per mol of the continuouslyintroduced fatty acid radical, and in vessel 1, 40%, in the vessels 2-4,20% each of this sulfur trioxide quantity was taken up. No sulfurtrioxide was blown into the last vessel, this vessel being used for theafter-reacting. The product running off from the last vessel was cooledand, after addition of 2 weight percent H2O2 (used as 40% aqueoussolution) was bleached for 2 hours at temperatures of 55-60 C. andsubsequently neutralized with 10% soda lye. The degree of sulfonation ofthe product was 95%. A 5% solution of the sulfonate, in reference tocrude acid sulfonation product, showed in the Lovibond Tintometer in a4l cell, the following color values:

Yellow: 6.0, red: 1.0, blue 0.0.

In a repetition of the example only 1.2 mol sulfur trioxide was used permol fatty acid radical, andthe temperature in the last reaction vesselwas increased to 85 C. The crude acid reaction product was bleached with2% of its weight H2O2 (used as 30% aqueous solution), and neutralizedwith 20% soda-lye. The product had a degree of sulfonation of A 5%solution of the crude acid sulfonation product showed, measured in theLovibond-Tintometer in a 4" cell, the following color values:

Yellow: 3.0, red: 0.3, blue: 0.0.

Example 2 As starting material a fatty acid ethyl ester, which had beenobtained from hardened coconut oil (iodine number=0.2) throughreesterilication with ethyl alcohol and distilling off of the fatty acidethyl ester was used. The sulfonation was carried out as in Example 1.The through-put of coconut oil acid ethyl ester amounted to g. per hour.The crude acid sulfonation product was bleached for 2 hours at 55-60 C.with 2% of its weight H2O2 (used as 40% aqueous solution), and thenneutralized with 15% soda-lye. The degree of sulfonation amounted to96%. A 5% solution of the crude -acid sulfonation product showed in theLovibond-Tintometer in a 4 cell the following color values:

Yellow: 6.0, red: 0.5, blue: 0.0.

Example 3 As starting material, the ethyl ester (iodine number=1) of ahardened and distilled tallow-fatty acid was used. This product wasprocessed in a similar manner Ias described in Example 1. 1.4 mol sulfurtrioxide per mol of ester was used. At the start of the test the sulfurtrioxide` was blown in, diluted with a 20-fold quantity of air, in suchquantities that in the first four vessels the followingv sulfur trioxidequantities were taken up (indicated in percent of the quantitiesstoichiometrically necessary for a quantitative sulfonation): 56, 84,112, and respectively. The reaction was then continued in continuousoperation with 151 g. ester put-through per hour. So much sulfurtrioxide wascontinuously introduced into the individual vessels that theabove-indicated sulfur trioxide quantities were dissolved in thematerial leaving the individual vessels.

The product running off from the last vessel was cooled and bleachedwith the addition of 4 weight percent H2O2 (used as 40% aqueoussolution), in the course of 2 hours at temperatures' of 55-60 C., andsubsequently neutralized with 15 soda-lye. The degree of sulfonation ofthe product was 93%; A 5% solution of the crude acid sulfonationproduct, showed in the Lovibond-Tintometer in a 4 cell, the followingcolor values:

Yellow: 10.0, red: 2.5. blue: V0.0.

Example 4 A distilled sec.butylester (iodine number=0.5), produced fromhardened coconut oil acid was used as the starting material. This`material was sulfonated in the manner described in Example 1 with athrough-put of 132 g. ester per hour with 1.57 mol S03 per mol fattyacid radical. The sulfur trioxide quantities taken up at the start ofthe test and during the same in the lirst four reaction vessels amountedto 63, 94, 133, and 157% respectively, of the stoichiometricallynecessary quantity for a quantitative sulfonation. No sulfur trioxidewas introduced into the last vessel and the temperature of this vesselwas maintained at 90 C. The sulfonation product was bleachedfor 2 hoursat 55-60" C. with 3% H2O2 and then neutralized with 5% soda-lye. Thedegree of sulfo-V nation of the product was 94%. A 5% solution of thecrude acid sulfonation product showed in the Lovibond- Tintometer in a 4cell, the following colorAvalues:

Yellow: 18,red: 2.5, blue: 0.0.

In a repetition of the example in which the temperature of the lastvessel was decreased to 85%, the degree of sulfonation of the productwas 90%, and the following color values were measured:

Yellow: 18, red: 2.0, blue: 0.0.

Example A mixture of 2500 g. ethylester of a hardened palmkernel fattyacid and 2200 g. hardened palm-kernel fatty acid was sulfonated in themanner described in Example 1. For this purpose, 117 g. of this mixture(iodine number=0.3) per hour were brought together with gaseous sulfurtrioxide, diluted with a -fold air quantity, wherein the 1.3-fold of theS03 quantity stoichiometrically necessary for a quantitativesulfonation, was used. The reaction vessels were kept during thesulfonation at the following temperautres: 50, 50, 65, 80, 80 C.respectively. The reaction product running olf was bleached for 2 hoursat 50 C. with 3% H2O2 (as aqueous solution), and then neutralized. Thedegree of sulfonation of the product amounted to 95 The color Lovibondvalues were:

Yellow: 6.0, red: 1.0, blue: 0.0.

Example 6 in the latter was used diluted with a 20-fold air quantity.

The temperatures in the vessels were, as also in Example 5, 50, 50, 65,80 and 80 C. respectively. The resulting reaction product was bleachedfor 2 hours at 55- 60 C. with 2% H2O2 (as 40% aqueous solution) and thenneutralized with 5% aqueous-soda-lye. The degree of sulfonation of theproduct amounted to 95.5%, the Lovibond color values were:

Yellow: 18, red: 3.0, blue: 0.0.

Example 7 As starting material, there was used apalm-kernel-fattyacid-ethylester (iodine number=0.l), which wasprocessed in an apparatus of stainless steel, similar in'all essentialparts to the apparatus described in Example 1 except the content of theindividual vessels to the over-flow amounted to 600 cm.

The first four reaction vessels were filled with the esterand theheating was so adjusted that the material in the vessels had during theentire test the following respective temperatures rising from vessel tovessel: 50, 50, 65, 80, 85 C.

Sulfur trioxide, diluted with a 20-fold quantity of air, was blown inthe rst four vessels in such quantities that the ester present thereinhad taken up the following sulfur trioxide quantities, measured at thestoichiometrically necessary quantity for a quantitative sulfonation:52, 78, 104 and 130% respectively. No sulfur trioxide air mixture wasblown into vessel 5. After these quantities had been taken up, 1.71 kg.ester per hour was continuously pumped into the first, and into thefirst four, reaction vessels so much of the above-mentioned sulfurtrioxide air mixture was introduced that the ester passing out of thefourth vessel had taken up in all 1.3 mol per mol of fatty acid esterand in the 1st vessel 40% and in the 2nd to the 4th vessels 20% each ofthis sulfur trioxide quantity had been taken up. No sulfur trioxide wasblown into the fifth vessel; this vessel serving for the after-reacting.

The product thus obtained was continuously bleached and for this purposewas rst of all cooled to 20-22 C. Then, 2420 g. per hour of the cooledproduct were mixed with 181 g. per hour of 20% aqueous hydrogenperoxide. The initially occurring reaction heat was removed in a coolerwhich the product left at a temperature of 40 -with the invention.

C. Thereupon the temperature was kept for 2 hours at 40 C. and thenstill a further hour at 60 C. The bleached product was neutralized with6% aqueous soda lye. The process was run continuously for 72 hours anddelivered a completely uniform product which had a degree of sulfonationof 95% and showed the following Lovibond color values:

Yellow: 2.0, red: 0.1,` blue: 0.0.

Example 8 The part-s a and b of this example demonstrate a continuousmode of operation falling outside of the scope of the invention forcomparison with part c in accordance As starting material, an ethylester (iodine number=0.2) produced from hardened fatty acids of thepalm-kernel fat was used. The tests described.

under a, b, and c were carried out in the same apparatus; however, inthe -tests a and b all parts -of the apparatus were kept at thetemperature there indicated.

(a) Into the reaction vessel 230 g. (0.92 mol) ester was charged andheated to 65 C. Then, within 100 minutes, 96 g. (1.3 mol) sulfurtrioxide, diluted with 20- fold quantity of air, were blown into theester. As soon as this sulfur trioxide quantity had been taken up, 125g. of ester per hour were added drop by drop and so much sulfur trioxideair mixture introduced that per mol ester 1.3 mols sulfur trioxide airmixture were taken up. 177 g. reaction mixture per hour flowed off fromthe apparatus. From time to time the receiver was changed and the degreeof Sulfonation and color values determined. The degree of sulfonationlay during the entire reaction between 82 and 83.5%. However, the depthof the color increased continuously and after 6 hours of voperationreached a nal value.

(b) The test described under (a) was repeated. However, the temperaturewas increased to 85 C. The degree of sulfonation of the product amountedto 94-95%. The color intensity increased during the course of thecarrying out of the test.

(c) The ester was sulfonated with the same sulfur-trioxide excess asunder (a) and (b). However, the temperatures in the individual reactionvessels were adjusted to 50, 60, 70, 80, and 80 C. respectively. Thedegree of sulfonation of the product was 95 Samples of the productresulting after 6 hours of carrying out of the processes 'were bleachedwith 2% H2O2 (used as 40% aqueous solution) for 8 hours at 30-40 C.Unbleached, as well as bleached products, werel neutralized in order tomeasure the color values of both. It was found that the colorvalues ofthe crude products obtained according to (a) and (b) could not bereliably measured'in a 4 cell. The product produced according to (c)had, in neutralized condition, measured as 5% solution in a 2 cell, thefollowing Lovibond color values:

Yellow: 27, red: 24, blue: 5.0.

The products neutralized after the bleaching with 2% H2O2 showed as 5%aqueous solution of the sulfonate in a 4" cell the following Lovibondcolor values:

In 126 g. of a hardened palm-kernel-fatty acid ethyl ester (iodinenumber=0.2) 52 g. sulfur trioxide, diluted with a 20-fold air quantitywere introduced in the course of one hour. The temperature was uniformlyincreased skilled artisan.

from 20 to 80 C. and the introduction velocity of the sulfur trioxidekept uniform during the entire time. After introduction of .the sulfurtrioxide quantity indicated, the product was still kept for minutes at80 C. The crude acid sulfonation product was bleached with 3% lof itsweight quantity of H2O2 (used as 40% aqueous solution) for 8 hours at30-40 C., and then neutralized with 8% soda lye. With a 5% sulfonatesolution, the following Lovibond color values were measured in a 4 cell:

Yellow: 1.3, red: 0.4, blue: 0.0.

The degree of sulfonatiou of the Iproduct amounted to 95.7%.

Example 10 In the manner described in Example 9, 113 g. hydrogenatedpalm-kernel-fatty-acid (iodine number=0.4) were sulfonated except thatthe starting temperature amounted to 35 C. A product with a degree ofsulfonation of 97% was obtained. The product, bleached as described inExample 3, had the following Lovibond color values:

Red: 27, yellow: 22, blue: 1.2.

While the invention has been described in detail with reference tocertain specific embodiments, various changes and modifications willbecome apparent to the The invention is, therefore, only intended to belimited by the appended claim-s or their equavalents wherein We haveendeavored to claim all inherent novelty.

We claim:

1. In the process for the sulfonation of a member selected from thegroup consisting of unsubstituted saturated fatty acids, unsubstitutedsaturated fatty acid esters, and mixtures thereof containing 6 to 28 Catoms in the fatty acid radical by reaction with gaseous sulfurtrioxide, the improvement which comprises initially contacting saidgroup member at a temperature between about 30 and 70 C. with about65-90% of a 1.1-1.8 molar quantity,

of gaseous sulfur trioxide based on the fatty acid radicals to besulfonated in at least one rst sulfonation step, and thereaftercontacting said group member in at least one l@ additional sulfonationstep with lthe balance of said molar quantity of sulfur dioxide at atemperature between about -95 C.

2. Improvement according to claim 1 in which said first sulfonation stepis effected at a temperature between about 40-65 C. and said additionalsulfonation step is effected at a temperature between about -90" C.

3. Improvement according to claim 1 in which said sulfonation steps areeffected at said temperatures and with said amounts of sulfur trioxide-in separate series connected reaction zones.

4. Improvement according to claim 3 in which said group member is passedsubstantially continuously in series through said zones,v and 1in whichthe sulfur trioxide is separately added lto said zones.

5. Improvement according to claim 1 in which said sulfur trioxide isused in admixture with an inert gas.

6. Improvement according to claim 1 in which said group member is anester of a fatty acid with a lower alcohol.

7.v Improve-ment according to claim 1 in which a total quantity ofl.21.6 mols of sulfur trioxide per mol of fatty acid radical to besulfonated is used and in which 70-85% of this sulfur trioxide quantityis added in the first sulfonation step.

8. Improvement according to claim 7 in which said group member contains12--18 carbon atoms in a fatty acid radical.

9. Improvement according to claim 7 in which said group member is anester of a fatty acid with a lower alcohol.

10. Improvement according to claim 1 in which said sulfonation isefected in the absence of a solvent.

References Cited by the Examiner UNITED STATES PATENTS 1,926,442 9/ 1933Gunther et al 260-400 2,691,040 10/ 1954 Bloch et al 260-400 v2,878,2713/1959 Little et al. 260-400 CHARLES B. PARKER, Primary Examiner.

DANIEL D. HORWITZ, Examiner'.

1. IN THE PROCESS FOR THE A SULFONATION OF A MEMBER SELECTED FROM THEGROUP CONSISTING OF UNSUBSTITUTED SATURATED FATTY ACIDS, UNSUBSTITUTEDSATURATED FATTY ACID ESTERS, AND MIXTURES THEREOF CONTAINING 6 TO 28 CATOMS IN THE FATTY ACID RADICAL BY REACTION WITH GASEOUS SULFURTRIOXIDE, THE IMPROVEMENT WHICH COMPRISES INITIALLY CONTACTING SAIDGROUP MEMBER AT A TEMPERATURE BETWEEN ABOUT 30 AND 70*C. WITHABOUT65-90% OF A 1.1-1.8 MOLAR QUANTITY OF GASEOUS SULFUR TRIOXIDE BASED ONTHE FATTY ACID RADICALS TO BE SULFONATED IN AT LEAST ONE FIRSTSULFONATION STEP, AND THEREAFTER CONTACTING SAID GROUP MEMBER IN ATLEAST ONE ADDITIONAL SULFONATION STEP WITH THE BALANCE OF SAID MOLARQUANTITY OF SULFUR DIOXIDE AT A TEMPERATURE BETWEEN ABOUT 75-95*C.